Background/Purpose: Rheumatoid arthritis (RA) is associated with an increased risk of myocardial infarction (MI) and post-MI fatality compared with the general population.  In a previous study examining post-MI treatment in RA compared with controls we noted that a higher proportion of the RA patients had experienced MI following a surgical procedure.  The aim of this study was to compare the incidence of MI and mortality (all-cause and cardiovascular (CV)) at 6 weeks and 12 months following joint surgery in patients with RA compared with the general population.

Methods: Individuals who had undergone joint surgery in Victoria, Australia between 1 July 2000 and 30 June 2007 were retrospectively identified from routinely collected hospital administrative data.  Individuals were classified as having RA using International Classification of Diseases codes recorded at the time of surgery or during any hospitalisation in the 2 years prior.  Incidence of MI and mortality at 6 weeks and 12 months post-operatively was determined from hospital data and linked death registry data.  Logistic regression analyses were performed with adjustment for age, sex, comorbidities, socioeconomic status and admission type (elective vs emergency).

Results: A total of 308,589 episodes of joint surgery occurred among 240,571 individuals, with 3654 (1.2%) occurring among patients with RA.  The RA cohort was older (mean (SD) age in years 62.4(13.4) vs 52.5(18.6)), with a female preponderance (74.6% vs 45.6%) and had a higher burden of comorbidities, lower socioeconomic status and fewer elective admissions compared to the non-RA cohort.  The number (prevalence) of events in the RA and non-RA cohorts respectively was as follows; MI at 6 weeks: 25 (0.68%) vs 838 (0.27%); death at 6 weeks: 22 (0.60%) vs 569 (0.19%); MI at 12 months: 59 (1.61%) vs 1968 (0.65%); death at 12 months: 93 (2.55%) vs 2411 (0.79%). 

Figure 1 shows the adjusted odds ratios (OR) for each of these outcomes in the RA patients compared with the non-RA patients.  At 6 weeks post joint surgery the adjusted OR of MI was 1.50 (95% CI 0.96-2.33), all-cause death was 1.87 (95% CI 1.12-3.11) and CV death was 1.93 (95% CI 1.10-3.39).  At 12 months post joint surgery the adjusted OR of MI was 1.71 (95% CI 1.28-2.29), all-cause death was 2.17 (95% CI 1.65-2.85) and CV death was 2.30 (95% CI 1.65-3.21). 

Conclusion: Following an episode of joint surgery RA patients have a significantly increased risk of death at 6 weeks, and MI and death at 12 months, compared to the general population.  The reasons for this remain to be elucidated but in the meantime RA patients should be considered at higher risk in the peri-operative period.

Figure 1 Risk of 6 week and 12 month myocardial infarction, all-cause death and cardiovascular death in patients with rheumatoid arthritis following joint surgery